A catastrophe. Labour lost Scotland, its heartland, the birthplace of its first leaders, by allying with the Tories in a campaign of fear during the referendum. Its supporters – many of whom, like their parents, grandparents, great-grandparents, had voted for Labour their whole lives – turned on their party. Labour became the detested “red Tories”, pillars of a political establishment with no roots in their communities. Voters have defected en masse to a party that positioned itself – certainly in rhetoric – to the left, with a populist anti-austerity message.

Yes, Labour’s Scottish collapse and the rise of the SNP enabled the Tories to cynically stir up English nationalism and resentment. Yes, the rightwing media, acting as the outright propaganda wing of the Tory party, ran a spiteful, venomous campaign. But the Labour leadership has to take the blame. They failed to even bother rebutting the narrative that they overspent in office, even though the Tories backed their spending pound for pound. While the Tories had a constantly repeated, clear, coherent message, Ed Miliband offered sometimes bizarre professorial speeches, failing to communicate in a way that resonated with voters. Even its natural supporters no longer knew what Labour stood for. Random policies were thrown into the ether – like increasing the minimum wage by 2020, effectively in line with inflation – while the leadership accepted the Tories’ underlying austerity message. The voters were never going to warm to Miliband, a product of a professionalised, technocratic elite. But his failure to offer a message of hope that was inspiring, credible or coherent has doomed his party to a calamity at the polls.

Where do we find a Nicola Sturgeon? That’s the question every political party bar the SNP must be asking itself. The night’s biggest scalps – from Jim Murphy to Danny Alexander – unquestionably belonged to her, but so arguably has this campaign. While every other national party leader has struggled to win voters’ trust, the SNP leader enjoys unwavering devotion; where they fought fearful, negative campaigns, she has connected with voters via an upbeat, hopeful message.

Whatever she’s got, her rivals badly need some of it; because as things stand she has brought the United Kingdom close to breaking point. A minority Tory government shored up by what’s left of the Liberal Democrats would have a toehold in Scotland, thanks to Alistair Carmichael and David Mundell surviving. But can it claim to represent a country that has so comprehensively rejected it? There are mutterings already from senior Tories about an urgent response to this looming constitutional crisis, although little sense of what that might be beyond Boris Johnson’s suggestion of some kind of looser-sounding “federal structure” – perhaps involving an English parliament for the English, alongside further devolution.

Sturgeon sounded defensive on the question of whether, by trouncing Scottish Labour, she has saddled her supporters with a Tory government they passionately didn’t want. It wasn’t her fault, she said tartly, that Labour hadn’t done well enough in England to take up her offer of a deal. Well, we’ll see if that returns to haunt her.

But, for now, the future of the union lies in the hands of David Cameron, a man who has proved willing to stoke English nationalism both in the aftermath of the independence referendum and during this campaign. This may not have been the last ever UK general election, but it no longer feels melodramatic to envisage that day.

Boris Johnson MP (again) said at his count that we didn’t need “fancy constitutional experts” to tell us what the election signifies. But that will not stop pundits, pollsters and political scientists sifting through this unexpected result more obsessively than any since 1992.

Even the most Panglossian, hyper-optimistic Tories I spoke to in the last 48 hours of the campaign thought that 290 was the upper limit they could reasonably expect. Planning a second interparty alliance, they were fixated instead on the likely Lib Dem outcome, and, specifically, Nick Clegg’s fate in Sheffield Hallam.

So now they are wondering, unexpectedly, exactly what went right. How did the party that failed to reach its own fiscal targets, that slashed 9% from departmental budgets, that allegedly presided over a “cost of living crisis”, that lost its hard-won credibility over the NHS with a disastrous plan, that has never quite shaken the image of the “nasty party”, hold on to power?

This is a vindication of Lynton Crosby’s insistence, long before the campaign proper, that the party identify a clear palette of issues and stick to it. In the determinedly straightforward formula devised by the Australian electoral consultant, Cameron offered “competence” versus supposed Labour chaos, and stress-tested leadership versus a man who could not handle a bacon sandwich, let alone HM government.

There were calls – I made one or two of them – for more vision, for more of what Bill Clinton calls “the future business”. But credit where it’s due: the “Lyntonisation” in which Cameron urged his colleagues to have faith delivered on the day. This was a referendum on trajectory (the country’s economic direction) and his character (who should occupy No 10).

Above all, the Tories had what the prime minister privately called the “human shield” of the Lib Dems. It was the coalition’s junior party that the electorate punished last night. The electoral blows slid off blue and on to yellow: again, and again, and again.

The Tories hung on by Faustian means, paying for success in the usual currency. But, ruthless to the end, they made sure that it was another party’s soul they traded.

The annihilation of the Lib Dems had long been predicted. Yet the procession of defeated MPs would have tugged at least a little at the heart strings of the most callous observer. Losing Charles Kennedy and Simon Hughes, the foundation MPs of the modern Lib Dems, first elected 32 years ago, is like seeing the pillars of Hercules crumble.

Across London, MPs for what in happier times was called the Thames riviera were scythed down – Vince Cable in Twickenham, Ed Davey in Kingston, Paul Burstow in Sutton and Cheam. In Scotland, the defeat of Jo Swinson early and Danny Alexander late bookended a terrible evening. The women and men who had served in the coalition, and their colleagues who had not, paid a heavy price.

Junior partners in coalition rarely prosper. But in scores of seats, the Lib Dems have come in behind the Greens. They had underestimated the cost of their decision to back the Tories five years ago. Recovery from that choice, which will surely now start with a leadership contest in the wake of Nick Clegg’s resignation later today, Friday, will take at least a generation.

The Lib Dems were as deceived by the polls as everyone else. When the real votes were counted the seats fell – in the south, to a sustained assault from their former partners in government, the Tories; in the north of England, it was Labour who feasted on their corpse, and in Scotland the SNP. It was even more brutal a plundering of the party’s electoral assets than it had suffered nearly a hundred years ago when they lost three quarters of their seats.

The collapse of the Lib Dems leaves space in the centre ground that Labour would do well to snatch. Ukip, the new insurgent, might have been disappointed not to have made more gains. But when the final share of the vote is confirmed, it is likely to fulfil Nigel Farage’s prediction that his party’s real challenge is to Labour. In the south, against Conservative opposition, it appears that Ukippers chose to retreat to the Tories rather than risk letting Labour in. But against Labour incumbents, in for example Southampton Itchen and Plymouth Moor, they seem to have sucked away the chance of Labour victories.

In the northern towns and cities of England they stacked up the votes, repeatedly knocking Tories into third place. Labour cannot let Ukip embed itself in what have been its heartlands for as long as there have been Labour MPs. The challenge for the party now, probably not one that Ed Miliband can meet, is to find a way of talking to the whole of a country that’s increasingly divided between north and south.